Low-grade industrial waste heat utilization in urban district heating: Simulation-based performance assessment of a seasonal thermal energy storage system

Abstract

In this study, a large-scale industrial waste heat heating system integrated with borehole thermal energy storage (BTES) and an absorption heat pump was proposed, designed, and assessed using long-term dynamic simulations. Simulations were performed with different reference combinations of storage volumes and circulation flow rates for the borehole heat exchanger, and a procedure for determining the optimal design parameters was demonstrated. The simulation results indicated that a large-scale BTES has significant potential for buffering short-term temperature variations in industrial waste heat recovery systems. The initial quasi-stable temperature of the BTES established itself gradually, and the energy input and output of the storage tended towards stability after 3–4 years of operations. The effect of increasing storage capacity tended to gradually decline with increasing circulation flow rate and storage volume after reaching a peak, becoming marginal at higher design parameter values. This result indicate that the storage volume and circulation flow rate of the system should be optimized according to an appropriate economic index, to maximize economic benefits. The simulation results emphasized the potential of large-scale seasonal BTES systems to be integrated with industrial waste heat recovery systems and district heating networks, to improve the stability of energy demand and efficiency.